Machine for producing screened



Nov. 20, 1953 J. A. BOYAJEAN, JR 2,575,546

MACHINE FOR PRODUCING SCREENED RELIEF PATTERN PLATES Filed July 24, 19484 Sheets-Sheet 1 2 E x q u E 5 g mar/50 70 MP5 27 FIG] INVENTOR. JOHN A.EOYAJEAN,J

ATTORNEY Nov. 20 1951 J. A. BOYAJEAN, JR 5 5 MACHINE FOR PRODUCINGSCREENED RELIEF PATTERN PLATES Filed July 24, 1948 4 Sheets-Sheet 2INVENTOR. JO H N A. BOYAJEAN (T':

ATTORNEY Nov. 20, 1951 J. A, BOYAJEAN, JR 2,575,546

MACHINE FOR PRODUCING SCREENED RELIEF PATTERN PLATES Filed July 24, 19484 Sheets-Sheet 3 FIG. 4b

INVENTOR JO N A. BOYAJ NJ; {3W

ATTORNEY Nov. 20, 1951 J. A. BOYAJEAN, JR 2,575,546

MACHINE FOR PRODUCING SCREENED RELIEF PATTERN PLATES 4 Sheets-Sheet 4Filed July 24, 1948 uOm Om 0 mwijas Em:

mmzz m o h h F M F W mm mm SEES? mwr=i2 5 mm o 0 M Q zmmmow 9 K E v tmm/\ |.|||l|| lllll J n? W mm mmw h 0 0 0 9 mwljlsz 5:513 3 H myuwasz b5201 9 1 $5 6m? 50-051; A o m A TE mm V0 a A N H o J WV ATTORNEY nodetailed description is required here.

i atentecl Nov. .20, 1951 MACHINE FOR PRODUCING SCREENED RELIEF PATTERNPLATES John A. Boyajean, Jr., Upper Montclair, N. J assignor toFairchild Camera and Instrument Corporation, a corporation of DelawareApplication July 24, 1948, Serial No. 40,594

27 Claims. 1

duplicating processes, it has been customary to A produce half-toneengravings, that is, engraving plates having a screen structure composedof a series of regularly spaced dots, by photo-chemical rocesses. Insuch half-tone plates, the average size and spacing of the dots in eachincremental portion of theplate vary proportionately with the averageshade value or greyness of the corresponding portion of the image. Thesurfaces of these dots lie in the original plane of the plate andreceive the printing ink from a roller or the like.

Such half-tone plates and their method of manufacture are well known inthe art, so that HOW- ever, it is also well known that the process ofmaking such photo-engravings involves elaborate and expensive equipmentand a large number of steps, each of which must be performed with greatcare and skill in order to obtain a satisfactory half-tone plate. Suchskill is generally acquired only by extended apprenticeship and artisansof the required skill are frequently unavailable. All of the foregoingfactors contribute to the high cost of such half-tone plates and to thetime required for their completion.

Heretofore there have been proposed various.

machines and apparatus for automatically and mechanically forminghalf-tone plates representative of an image to be reproduced. suchmachines have generally included a support for an image sheet, a supportfor the plate to be formed, and mechanism for scanning the two supportssynchronously. The image sheet scan ner. has included a photoelectricpick-up, the output of which is amplified electrically and utilized toactuate some type of plate-cutting or deforming tool carried by theplate scanner. An interrupter is included at some point in the system'.to produce the screen structure. In one previously proposedarrangement, the platedeforming tool is in the form of a heated stylusacting on a plate of decomposable material but, in general, suchproposed machines have utilized metal plates-and the deforming tool hasbeen a high speed rotating cutter or chipping or gouging tool. With thistype of apparatus, the tool generally leaves small burrs or otherirregularities over the face of the plate which seriouslyinterferes withobtaining satisfactory reproduc tions. Furthermore, the metal platesused in such machines are generally heavy, costly, and difiicult to shipand are easily damaged by improper handling.

Furthermore, the automatic machines for forming such half-tone platesheretofore proposed have been complex and cumbersome in operation andhave been difficult to maintain in accurate adjustment, which isnecessary to procure half-tone plates of reasonable cost andsatisfactory quality.

It is an ob ect of the present invention, therefore, to provide a newand improved machine for producing screened relief pattern plates whichobviates one or more of the above-mentioned disadvantages of theprior-art machines of the type described.

It is another object of the invention to provide a new and improvedmachine for producing screened relief pattern plates which achieves oneor more of the following advantageous characteristics not hithertorealized: virtual elimination of skill or technique in operation of themachine; substantial reduction in time required to form a plate; abilityto form a number of plates simultaneously; extreme accuracy ofreproduction of all image shades; elimination of all chemical andphoto-chemical processes; predetermination of the desired contrastrange, that is, range from full white to full black; and a substantialreduction in the weight of the formed plates.

In accordance with one feature of the invention, there is provided amachine for producing on a plate from an image sheet a screened reliefpattern suitable for image reproduction by printing processes comprisinga first cylinder for supporting a plate, a second cylinder forsupporting an image sheet, and means for rotating the cylinderssynchronously. The machine further comprises a first reciprocablecarriage including an electro-optical pick-up system disposed forscanning an image sheet on the second cylinder,- a second reciprocablecarriage including a platedeforming tool disposed for scanning a plateon; the first cylinder, means responsive to the output of the pick-upsystem for actuating the platedeforming tool, and means forreciprocating the; carriages synchronously. The machine also includes anelectrical screen generator including a rotor element drivensynchronously with said cylinders and an independently rotatable stator,and means for rotating said stator at a speed of a lower order ofmagnitude than said rotor element, the output of said generator beingconnected to modulate the output of said pick-up system. ,7 a n In thepreferred'embodiment of the invention, the engraving machine optionallyincludes other desirable features, among which are the following: theelectro-optical pick-up system includes a light source and a source ofpuisatn g gne c of screen frequency, such as the screen generator,connected for modulating such light source; in order to form on theplate an inverted image of that on the image sheet, the pick iip'syst'emcarriage and the tool carriage are driven by atensioned inelastic belt,one of the carriages being adapted to be locked to one run of the beltand the other bein provided with a releasable clamp to-enga'ge theotherrun of the belt; further, the

tool carriage comprises a tool-actuating assembly carrying theplate-deforming tool and means for biasing the tool' assembly intoengagement with the plate-cylinder; the tool assembly also includes anadjus'tahbl'e shoe engaging a plate onthe plate cylmder for determiningthe neutral position of thetool.

In accordance with another feature er a preferredfo'rm of theinventiom'a machine of the type described includes means for adjustingthe output of the "screen generator to adjust the minimum deformation ofthe pl'ate, corresponding to the black level of an image sheet, andmeans-foradjusting-the output of the pick-up system substantiallyindependentlyto' adjust the maximum deformation of the plate,corresponding to the white level of an image sheet.

"Another feature of the-preferred form of the invention comprisesmeans'for biasing the platedeforming tool to an inoperative position, anormally excited electromagneticmeans for retaining thetool in anoperative. position, and means responsive to the failure of the sourceof periodic screen potential, such as the screen generator, foractuatingthetool to an inoperative position.

For a better understanding of the present invention, togetherwithother'andfurther objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will bepointe'd out in the appended claims.

Referring now to the drawings, Fig. 1 is-a schematic perspective of amachine for producing on a plate from an image sheet a screened reliefpattern suitable for image reproduction by printing processes; Fig. 1ais a chart to aid in explahation of the operation of "the machine ofFig. 1; Fig. 2 is a fragmentary view, partly in section, of theplate-defo'rming tool assembly ofthe machine of Fig. 1 together with anassociated stroboscopic vie'wer; Figs. 3a and 3b are schematicperspective views of the tool-actuating mechanism in its neutralposition and one extreme position, respectively; Figs. 4a and 4b are topplan and longitudinal 'elevational views, respectively, of themachine'represented in Fig. 1; while Fig. 5 is a schematic electricalcircuit diagram of the various electrical and electronic components ofthe machine of Fig. 1.

tions of the surface are removed, the area of the removed portions inany elemental portion of the print varying with the shade values of thecorresponding elemental portion of the image to be reproduced, the be'stknown example of such a screened relief pattern being the half-tonephoto-engraved plate. By the term printing processes, as used herein andin the appended claims, is meant any process by which a plate carrying ascreened relief pattern may be utilized to produce multiple reproducedimages, of which the most usual example is the'conventional printingprocess.

The machine of Fig. 1 includes plate andeimage sheet supports,specifically, a cylinder Hlon which is supported or secured in anysuitable mannera plate ll of deformable material and a "second cylinderI2 on which is supported or secured :an image sheet [3. By the termdeformable material is meant a material that may be cut, gouged,decomposed or otherwise deformed byan engraving tool or stylus to forman image re producing plate. The plate and cylinder assembly H), Il maybe of any suitable type-but preferably is of the'type-describe'd andclaimed in applicant's copending application, Serial No. 40,595, filedconcurrentlyherewith. The image sheet I3 for usein the machinespecifically :described hereinafter is :a :photographic positive print.

The machine of Fig. 1 includes means-for rotating the cylinders 10 and12 synchronously and preferably isochronously. Specifically, thisrotating means includes a-common shaft for the two cylinders includingportions (1,441) coupled by a disengageable coupling i5. The couplingl-5 includes a notched disc l5arand, a complementary disc [517 providedwith a pin l'5c adap ted accurately to engage the notch of disc l5a whenthese Referring now more particularly to Fig. l'of the drawings, thereis illustrated schematically a machine embodying the invention forproducing on a plate from an image sheet a screened rcllefpatternsuitable for 'imagereproduction by discs are moved axially by a lever"l5dto effect engagement of the coupling. This pin-type coupling ensuresengagement'of the two shaf-t portions Ma, Nib in a predetermined phaserelationship so that they rotate isochronously. The shaft I ia isconnected to be driven by a motorlt which may be of any suitable type,althou'ghifa number of machines are to be operated in mul tiple, asdescribed hereinafter, the motor must be of the synchronous type. Thedriv-ing connection from the motor iii-to the shaft Ma -in:- cludes aflexible coupling ll ofranysuitabl'e type which mechanically filters orsmoothes out any pulsation characteristic of the driving motor 16. Thisdriving connection further includes a'worm i8 and engaging worm gear l9and anovr=run=- ning or one-way driveclutchifl, the driving element ofwhich is connected to gear [9 'and:the driven element of'whichisconnected-to shaft'lda. On the drive shaft kid is aheavyfi'y"wheel 21 which ensures pulsationles rotation'of 'the sha'ft Ma, lb andthe cylinders I'O'an'd l'2regar'dless of irregularities which :mightotherwise result from the characteristics of the motoricon-linperfecti'ons 'in the drivingsgears. The over rtnrning clutch 2B,which-maybe'of'anyconventional type, 'serves two purposes: ('1)itallows' thefifiy wheel 2| to decelerate normally upon de-cnerglzationof the driving motor I6 without imposing an undue back load on thespeed-reducing gears 18,19 and (2) it permits manual rotation of thecylinders ill and i2 during mounting of the respective plate ii andimage sheet l3 thereon, free of the driving gearing.

The machine of Fig. 1 also includes means, such as a reciprocablecarriage 22 including an electro-optical system, for scanning an imagesheet l3 on its supporting cylinder [2. The electro-optical scanningsystem is shown schematically as including a light source 22a having anoptical system 221) and a photocell 220 provided with an optical system22d including an aperture stop to limit its field of view to anelemental area of the image sheet i3 and is disposed to receive onlydiifused reflection, that is, the angle of incidence of the axis ofoptical system 22b at the image sheet i3 is not the same as the angle ofreflection of the axis of the optical system 2211. The machine furtherincludes means, such as a reciprocable carriage 23 including aplate-deforming tool 24, for scanning a plate H on its supportingcylinder ill. By the term plate-deforming tool, as used herein and inthe appended claims, is meant a tool capable of deforming a plate II asby cutting, gouging, indenting, there mally decomposing, or the like. Inthe preferred embodiment of the invention, the tool 24 is a heatedstylus for thermally decomposing incremental areas of the surface of theplate II, as described hereinafter. The carriages 22 and 23 reciprocateon parallel longitudinal guide rods 38 and 39.

There is further provided a mechanism for reciprocating the carriages 22and 23 in opposite directions to form a laterally inverted screen reliefpattern on plate li. This mechanism includes a pair of spaced pulleys 25and 26 and a tensioned inelastic belt, such as a steel tape 21,supported on the pulleys. Tensioning of the tape 21 is effected by astiff helical spring 28 joining its two ends. The pulley 25 is drivenfrom shaft [4a through double worm gearing 46, 41 and 48, 49, the gearratio being preferably so chosen that the pulley 25 makes one revolutionfor the complete normal range of travel of the carriages 22 and 23. Oneof the carriages, preferably the carriage 23, is adapted to be locked orsecured (by means not shown) to the lower run of the tape 21, while theother carriage 22 is provided with a releasable clamp disposed to engagethe upper run of the tape 27 and including a manually operable elementor knob 29, by which the carriage 22 can be released from the tape 2! topermit adjustment of the carriage 22 independent of the carriage 23 upondisengagement of the pin coupling 15. This adjustment is provided topermit accurate registration of the electro-optical system of thecarriage 22 with an image sheet l3 on the cylinder i2 when initiallysetting up the machine.

The carriage 23 includes a tool-actuating assembly 3G for driving theplate-deforming tool 24. As shown in Fig. 2, the assembly 30 includesmeans for determining its neutral position with respect to the plate Hon the cylinder ill. This means is in the form of a resilient hairpin 3!having one arm secured to the assembly 30 and carrying at the end of theother arm a shoe 32 disposed to engage a plate I l on the cylinder Ill.The separation of the arms of the hairpin 31 may be adjusted to adjustthe neutral position of the shoe 32 by means of a thumb nut 33 threadedin the other arm of the hairpin 3|.

The tool-actuating assembly-30 also includes means for biasing the toolto an inoperative position.- To this end, the assembly 30 is mounted ona platform 34 which is pivoted on the carriage 23 as by a pivot pin 35.About the pivot pin 35 is secured a stiff helical biasing spring 36 withextending portions acting on the platform 34 and carriage 23 to bias thecarriage 33 for pivotal movement in a clockwise direction about thepivotpin 35. Secured to the under side of the carriage 23 is anelectromagnet 31, for which the pivoted platform 34 acts as an armature.As described hereinafter in connection with the circuit diagram of Fig.5, the electromagnet 31 is normally excited to attract the platform 34and retainthe shoe 32 and the tool 24 in an operative relation withrespect to the cylinder [0 and plate I l. The tool-actuating assembly 30also includes electromagnetic means connected to respond to the outputof the electro-optical pick-up system 22a-22d for actuating the tool 24.This electromagnetic actuating mean is shown more clearly in Figs. 3aand 3b, while its connection to the electro-optical pick-up system isdescribed hereinafter with reference to the complete circuit diagram ofFig. 5.

The machine of Fig. 1 further includes a source of periodic pulsatingpotential or current, specifically, an electrical screen generator 40driven synchronously with the cylinders 10 and I2 and connected tomodulate the output of the pick-up system 22a22d for producing apulsating excitation of the actuating means 30 at a screen frequency.Specifically, the generator 40 includes a toothed rotor element 40a,mounted on and driven by the shaft 14a, thus eliminating any-back-lashin the drive of the screen generator and ensuring absolute accuracy inthe spacing of the screen dots. The generator also includes. anindependently rotatable toothed stator element 401). The teeth of theelements 40a and 40b are equally spaced about the outer and innerperipheries thereof, respectively, the number of teeth in each beingdetermined by the desired screen. For example, if a 12G-screen plate isdesired, each of the elements 40a and 40b will have /2 teeth within anangle of rotation corresponding to a peripheral travel of the stylus 24of one inch on the plate i i. The elements 40a and 40b are electricallyinsulated from each other and are connected in an electrical circuit toform the two elements of a condenser, as described hereinafter inconnection with the complete electrical'system of the machine.

. There is also provided means for rotating the stator element 401) at aspeed of a lower order of magnitude than the rotor element.Specifically, there is provided a speed-reducing means between theshaftv Ma and stator element 431). This means includes a pulley 41mounted on a shaft 42 supporting the stator element 3%. Driving thepulley 4 lis an endless belt 43 passing around a pair of guide pulleys44 and a return pulley 45 disposed so that the upper run of the belt 43is parallel with the path of movement of the carriagez23. The belt 43 isconnected to be driven by the carriage 23 as by a connection 43a, asshown, and includes a tensioning spring 46 on the return side of itsconnection 43a. Adjustment of the speed ratio may be determined byselection of the diameter of pulley 4! relative to the lead of thecarriage 23. The overall reduction is such that the speed of the statorelement 40b is a small fraction of the speed of the 15 cylinders wandl2. If a plate is desired in which the angle oi. the screen lines is45". as iscustom'ary, the speed of the stator element '40!) is thatJfraction of the speed ofthe-cylinders land 12 such that the stator 40brotates an angular distance equal to one tooth and space during the timethat the cylinders l and I2 make two complete revolutions. I

.The details of construction ofthe stylus actuating mechanism 30 arebest shown in'th'e 'schematic perspective views, partly in section, ofFigs. 3a and 32). As shown, the'magne'tic circuit of the mechanism-30 isformed by two spaced opposed C-magne'ts 30a and 391). symmetricallydi'sposed in the air gaps formed between the opposed legs of theC-ma'g'nets 30a. and 30b is a vane-like magnetic armature 36c abouteither end o'f Which are disposed the actuating windings 30c and 3011,thus providing a balanced electromagnetic actuating'mechanism.

In Fig. 3a the armature 30a is shown in the unexcited or neutralposition, while 'in Fig. 31) it is 'shown in one limiting actuatingposition corresponding to maximum excitation of the windings 30c and GMof one polarity. extension of armature 35a is connected to the stylus 24which is loosely supported for reciprocation in a projection '30:! ofthe casing 39. Surrounding-the stylus 24 is a noninductive heater 56connected to and supported by terminals 51. 'The casing of the mechanism'38 comprises a permanent magnet'structure in which the side plates- 30fand 30g are permanent magnet elements, while the end plates completetheir magnetic circuit through the C-members 30a and 38b. The armature30c i mounted on a tension shaft 36h, rigidly supported from the casing.In Figs. 3a and 3b the dotted lines indicate the-paths of the permanentmagnet fiux in the two positions of thea'rmature member, while the dashlines representthe paths of flux due to the actuating windings 30band'3llc.

The actual physical construction of one embodiment of the apparatusrepresented :in Figs. 1 and 2 is shown in Figs. 4a. and 4b in whichcorresponding elements are identified by the same reference characters.Briefly, the whole apparatus is mounted'on a base or bed plate so, thegearing l8, l9 and cent, the pulley '25, the flywheel 2i, and the screengenerator ii) being renclosed within an end housing i The actuatingmechanism 383 is enclosed within a housing .52 mounted on carriage 25,while theelectro-op'tical pick-up system is disposed within a housing:53 mounted on carriage 22. The-pin clutch, 1.5 is disposed within acentral bearing support 154 which includes the pin clutch l5 and-itsoperating lever Had. The unit 54 also includes electrical switches andcontrol members for the electrical system of the machine describedhereinafter. The pulley 25 and the bearing for the right-hand end of theshaft l lb are disposed in an .end housing 55. It will be understood,however, that the details of this mechanical construction andarrangement may be varied within wide limits to suit individual specialrequirements.

Referring specifically to Fig. 2 of the drawings, there is shownassociated with the cylinder in and plate It a stroboscopic viewerforzinspecting a plate while it is undergoing deformation. This viewerincludes a portable microscope 60- disposed on a support ii adjustablypivoted at 62 on a base $3 and thus adjustable for focusing-on a plateH. The microscope fill is included within an enclosing housing: 64 whichalso includes a stroboscopic light source, suchas a gaseonslamp- 65andan optical system'fifiifor iocusi-ng'the light *78 'with the maximum andminimum shadevalues':

upon an elemental area of the plate ll being examined. The lamp '65is-connected to a circuit for exciting it from the periodic source orscreen generator 453, as described hereinafter.

Referring now to'Fig. 5 of the drawings, there is represented a circuitdiagram, partially schematic, of the electrical system of the apparatusof Fig. 1, corresponding elements being identified by'the same referencecharacters. Starting with the pick-up photocell 220, this is representedas a device of the conventional electron multiplier type, in which theseveral multiplier cathodes 229 are connected to electrically spacedpoints on a voltage-divider resistor 55 connected between ground and thenegative terminal of a unidirecnetwork l5, constituted for example by aseries resistor 15a followed by a shunt condenser 15b, is connected fromthe output terminals of the amplifier '73 through a coupling condenserit to the input terminals thereof for eliminating the effect on theoutput signal of variations of the mean brightness of an image sheet onthe mean position of the stylus 2 2. As well understood in the art, suchan inverse or negative feedback of the low frequencies reduces the gainof the amplifier at such frequency to a very small value withoutappreciably affecting its response to the high-frequency components ofthe signal generated by the photocell 220.

The periodic source of generator 40 is connected to modulate the outputsignal of the pickup system developed across the load resistor 14. Tothis end, the generator 5i] is connected as a variable condenser in theinput circuit of a screen amplifier unit ii; specifically, the rotor isconnected to ground while the stator is connected to a source ofpolarizing voltage +B through an isolating resistor ltd. The output ofamplifier llis coupled through a condenser 18 to an additional amplifierunit 39, the output of the amplifier 19 being connected through acoupling condenser Bil to a load resistor 8| provided with an adjustabletap or connection-82. the tap 82 is applied to a scanner light amplifier84, which is power amplifier for generating a periodic currentsynchronous with the periodic potential developed by the generator Ail.The current output of the amplifier 84 is connected to modulate thelight source 22a of the pick-up system; specifically, the lamp 22a maybe connected directly in the output circuit of the amplifier 84 to beexcited thereby.

A second load resistor 85 is included in the outputcircuit of amplifierl9 and provided with an adjustable tap 86 from which a selected portionof theoutput signal is applied to a strobelight. amplifier 8?, which isalso a power amplifier ford'eveloping a periodic current pulsesynchronous with the periodic potential generated by generator #9. Thegaseous discharge lamp of the stroboscopic vieweris connected directlyin the output of the amplifier 8i.

Inorder to permit a ready adjustment of th maximum and minimumpenetrations of a plate l i being deformed by the stylus 2 3 inaccordance The signal at.

of the image being reproduced, there is provided a circuit for combiningan adjustable portion of the output of the screen generator 40 with anadjustable portion of the output from the photocell 220 to energize theactuating mechanism 30. To this end, the output of the amplifier TI isapplied also through a coupling condenser 88 to a load resistor 89having an adjustable tap 90. The load resistor I4 of the amplifier I3has an adjustable tap 9I and the taps 90 and BI are interconnectedthrough isolating resistors 92 and 93 and a switch I05, the junction ofresistors 92 and 93 being connected to an isolating amplifier 94 which,in turn, is connected to a power amplifier 95, the output of which isconnected through a power transformer 96 to the serially connectedwindings 30c and 30d of the stylus actuating mechanism 30. In case itshould be desired to operate the machine of the invention from aseparate synchronized source of image signals from a local or remotesource, there may be provided a voltage divider I03 having an adjustabletap I04 and connected to the source or supply terminal I06 at which suchsignals appear. The switch I05 may then be operated selectively toconnect with the tap I04 or the tap 9|.

In series with the windings 30c, 30d is a dropping resistor 91 having anadjustable tap 98, while across the secondary winding of transformer 96is connected a voltage-divider resistor 99 having an adjustable tap I00.The taps 98 and I are interconnected through isolating resistors WI andI02, the junction of which is connected back to the input circuit of thepower amplifier 95. From the tap I00 is derived a signal potential whichvaries with, and is a fraction of, the potential across the actuatingwindings 30c, 30d, while from the tap 98 is derived a potential varyingwith the signal current through the windings. These two signals arecombined and fed back to the input circuit of amplifier 95 as an inversefeedback for linearizing the overall characteristics of the amplifier 95and actuating mechanism 30 and for effectively controlling the outputimpedance of amplifier 95 to obtain a desired degree of damping of theactuating mechanism 30. The unidirectional sources for the severalamplifier units of the circuit of Fig. are represented collectively as+B, although the sources of the several amplifiers may be of differentpotential values according to the tube types and circuit constants ofeach amplifier. It will be understood that each of the severalamplifiers described may be of any suitable conventional type of one ormore stages, as required.

The general electrical power circuit for the system is represented atthe top of Fig. 5. Power for the unit as a whole may be conventional60-cycle, l-volt power applied to the input terminals H0. The lowerterminal I I0 is connected to a bus III common to the power and controlmechanisms hereinafter described. The upper terminal I I0 is connectedto a control line II2 through a manually operable off-on switch H3; 9.pair of limit switches I I4 and H5 disposed in the path of travel ofcarriages 22 and 23 (not shown) for interrupting the electrical circuitin case either carriage reaches its limit of travel; the normally opencontacts I I 6 of a safety microswitch mounted on the platform 34 andadapted to be closed initially by manual operation of the tool-actuatingassembly 30 to operative position to complete a holding circuit forelectromagnet 31; normally closed contacts of a push button stop switchI I8; and the normally closed control circuit tacts I I9 of a relay I20. The relay I 20 is connected in the anode circuit of a vacuum-tubeamplifier I2I, the control electrode of which is connected to the outputcircuit of amplifier l9 and includes a conventional grid leak I22 andgrid condenser I23. The relay I20 and amplifier I2I are adjusted so thatthe relay I20 maintains its contacts closed whenever normal potential issupplied from the screen generator 40 through the amplifiers I1 and 19.Thus, the elements I20, I2! constitute means responsive to the failureof the source, specifically, to the failure of rotation of the generator40, for interrupting the con- II2, which de-energizes holding magnet 31,permitting the biasing spring 36 to actuate the tool 24 to inoperativeposition.

The contacts I I9 of relay I20 complete a circuit to the holding magnet31 of the actuating mechanism 30 through a resistor I24 and a rectifyingdevice such as a contact rectifier I25, the winding 31 being by-passedby a condenser I26. Connected between the buses I I I and I I2,immediately following the oif-on switch I I3, is a current transformerI21, the primary winding of which is connected in series with aconstant-current ballast tube I28. The secondary winding of transformerI2? is connected directly to the heater 56. Following the contacts II6of the safety switch, the motor I6 is connected between the buses IIIand I I 2. While the motor I 6 may be of any suitable type, it is shownas a split-phase condenser motor of the hysteresis synchronous type,having one winding IBa connected directly between the power buses and asecond winding IBb connected therebetween through a phase-splittingcondenser I29. At this same point, a power rectifier unit I30 isconnected between the buses III and H2. The unit I 30 may be of anyconventional type for converting the alternating-current supply to aunidirectional current of required operating potentials, indicatedcollectively by the reference +B.

Coming now to the operation of the apparatus described and referringfirst to the mechanical operation of the apparatus of Fig. 1, it will beseen that initially a plate to be engraved or deformed is mounted oncylinder I 0 in any convenient manner, as by the method described inapplicant's aforesaid copending application, Serial No. 40,595. The pinclutch I5 is disengaged and the image sheet is then mounted on cylinderI2 in any suitable manner. For this purpose, the carriage 22 may beunclamped from the belt 21 by means of the release knob 29. The carriage22 may then be adjusted longitudinally to obtain proper registration ofthe pick-up system 22a22c with the image sheet. The pin clutch I5 isthen engaged to ensure a direct driving connection between the shaftportions I 4.41 and I4?) and further to ensure correct phasing of thecylinders I 0 and I 2.

The cylinders I0 and I2 may be manually rotated by virtue of the slipclutch 20 and the mechanism may be operated until the stylus 24registers with a margin of the plate to be engraved. The stroboscopicviewer shown in Fig. 2 is then disposed to obtain a microscopic view ofthe elemental area of the plate II in registry with the stylus 24 and,with the electro-optical system in operation as described hereinafter,the deforming or decomposing of the plate II by the stylus 24 isobserved when the electro-optical pick-up system views the darkest andlightest portions of the image sheet to be reproduced. Adjustments ofthe electrical system are then I 1 made, as described hereinafter, toobtain the appropriate minimum and maximum penetrations of the plate Hby the stylus 24 corresponding to the darkest and lightest shade valuespresent in the image sheet, respectively.

The cylinders It and F2 and their associated mechanism are then operatedmanually to place the eIectro-optical pick-up system at the startingcorner of the image to be reproduced. The electrical system is then putin operation and is effective automatically to cause the electro-opticalpick-up system 'to scan the image sheet in a spiral path andsimultaneously to cause the stylus 24 to scan theplate II. While thecylinders H and l2' are effectively on a common shaft, so that theyrotate isochronously in the same direction, the carriages "22 and 23move at equal speeds in opposite directions, due to the fact that theyare clamped to opposite runs of the tape 21, as described above. Theresult is that the image reproduced on the plate H is laterally invertedwith respect to the image sheet, so that when it is turned over it willreproduce the image in its correct relation.

Rotating simultaneously with the cylinders H1 and I2 and at the samespeed is the rotor element 46a of the screen generator 45. Thisgenerator, as described hereinafter, is effective to modulate the lightsource 22c of=the electro-optical system and the constants of the systemare selected so as to procure substantially complete modulation, thatis, so that the light source 220. is substantially completelyextinguished at the fr quency of the screen "generator. The output ofthe'photocell 220 is thus likewise modulated and, after amplificationand the suppression of the unidirectional component, is applied as asignalmodulated'carrierwave to the 'windings 36c and 30d of. theactuating mechanism 30. This excitationof the windings 30c and 30dcauses the stylus to oscillate aboutits "mean or neutral position at thefrequency of the signal developed by the screen generator All, while theamplitude of the oscillation is varied or modulated in accordancewithgthe amplitude of the signal developed by the photocell 226' which,in turn, varies with the shadevalues in the successive incremental areasof the image sheet being scanned. As stated above, the plate If ispreferably of a decomposable material, such' as cellulose nitrate, whiler the stylus 24 is heated to a temperature of the order of 1200- F. bythe heater 55 so that, as it oscillates into contact with the plate H,the stylus removes portions of the plate by thermal decomposition;formin pits of depth and surface areavarying with the amplitude of theoscillation of the stylus 24" andthus with the variations in the shadevalue of the image sheet. As jaresult, there is formed on the surface ofthe plate H the equivalent of a half-tone structure comprising a seriesof elemental dots separating gieries of. pits formed by the oscillatingstylus F'or proper image reproduction, the screen structure of the plateII should, for the lightest shade presented in the image beingreproduced, contain a complete series of dots or islands separating thepits but of minimum area. Con versely, when scanning the darkest portionof the image sheet, a complete series of pits of minimum surface areashould be formed. In order to secure this result, certain adjustments ofthe electrical system are made, as described hereinafter, to ensure thatthe amplitude of the pulsating excitation from the screen generator i240 isso proportioned to the constantsof' the actuating means 39 that thefollowing relationships are satisfied: I

(1) The mean penetration of the plate H by the tool 2A; is of the sameorder of magnitude as the neutral separation of the tool and the plate.I

(2) The amplitude of the pulsating excitation from the screen generatorit is so proportioned to the response of the electro-optical pick-upsystem that the minimum penetration of the tool, corresponding to oneshade extreme in the image, for example, black, is of the order of ofits maximum penetration, corresponding to the other shade value, forexample, white.

(3) The rotational pee'dof the cylinders l6 and I2 is so related to thefrequency of excitation from the screen generator 46 that the peripheral travel of the plate cylinder it during one period of thescreen-frequency excitation is approximately twice the line spacing. Forexample, if it is desired to produce a 120-line half tone plate, thecylinder iii should travel 1/ 60\/2 inch during one period or cycle ofthe screen frequency. v

The foregoing relationships are represented in Fig. 1a, in which theline b represents the devel opment of the surface of plate I 1, whilethe line ('1.

represents the relative path of travel of the neutral position of thetool 24. In this figure, curve 0 represents one cycle of screenfrequency modulated to minimum amplitude corresponding to a black shadein the image being-scanned, while curve (1 represents another cycle ofthe screen frequency modulated at maximum amplitude corresponding to awhite portion of the picture being scanned. The relative dimensions ofthe various parameters of one machine embody ing the invention arerepresented in Fig. 1a and it will be seen that these relativedimensions satisfy the first two of the foregoing relations; that is,the excursion of curve 0 below the line b, representing the minimumpenetration of the stylus, is approximately one-fifth the ex cursion ofcurve (1 below line 1), representing the maximum penetration of thestylus, while the mean value of these two excursions is of the sameorder of magnitude as the separation of the lines a and b representingthe neutral sep-- aration of the stylus and the plate. It will also beseen that, since the unidirectional component of the modulated signal issuppressed so that only a pure alternating current signal is applied tothe windings of the actuating mechanism 3t, only the negative half ofeach cycle of screen frequency is effective to actuate the tool 24 intopenetration of the plate H. Therefore, the surface of plate 1 I oncylinder ill must travel a distance equal to the spacing of adjacentlines in the period from the commencement of one negative half cycleeffective to form a pit of one line to the successive negative halfcycle effective to form the next pit. This satisfies the thirdrelationship above.

Turning now to Fig. 5 of the drawings, there will be taken up theoperation of the electrical system of the machine of Fig. 1. In order toplace the machine in operation, the on-off switch H3 is initiallyclosed. This energizes the heater 56 through the current transformer l2?and the heaters of the various electron tubes. With the limit switchesH4, H5 normally closed and aftera reasonable warm-up time, the toolactuating assembly 30 is manually lowered to operative position.contacts H6 are closed, and the motor I6 is placed in operation to drivethe various mechanical elements of the machine of Fig. 1, including thescreen generator 4%. Simultaneously, the power rectifier I30 isenergized and supplies at its output terminals +B suitableunidirectional potentials for the several amplifiers of the system. Whenthe apparatus has reached normal speed and the power rectifier is inoperation, the screen generator 40 is effective to develop a periodicpotential of the desired frequency which is amplified in the units 11and I9 and applied to the grid of amplifier tube l2l. Initially tube I2!has zero bias and is fully conductive, energizing relay I to hold openits normally closed contacts. However, when the screen-frequency signalis applied to the grid of tube I 2|, it is self-biased by gridrectification substantially to cut-off de-energizing relay I20 to closeits contacts H9. Up to this time, the platform 34 must be held downmanually. Upon the closing of contacts H5 and H9, however, theelectromagnet 37 is energized with unidirectional current through therectifier I25. The electromagnet then attracts its armature 34 to holdthe actuating mechanism into engagement with the plate H on cylinder I0. The machine is now in full operation for forming an image on theplate H.

As stated above, initially the tool 24 is operated to a margin of theplate H for forming a test pattern on such margin, while observed by thestroboscopic viewer, as shown in Fig. 2. The neutral position of thetool 24 is adjusted by adjusting the shoe 32 by the knob 33 (Fig. 2) tothe desired relation, as represented in Fig. la. In view of the factthat the output of the screen generator 40 as amplified in units H, 19,and 81 is applied to the gaseous discharge lamp 65 of the stroboscopicviewer, this lamp illuminates in synchronism with the lamp 22a of theelectro-optical pick-up system, so that the elemental portion of theplate ll being viewed is illuminated only for brief intervalssynchronous with the peaks of the modulated screen frequency, this is,with the points of maximum penetration of the tool 24. As is wellunderstood in the art, the observer thus obtains an apparentlystationary view of the minute portion of the plate penetrated by thetool 24.

Initially the minimum penetration or deformation of the plate isadjusted to correspond to the black level or darkest shade in the imagesheet being scanned. This initial adjustment is made by tap 99 ofvoltage divider 39 which adjusts the minimum amplitude of thescreen-frequency signal amplified and applied to the actuating mechanism35. This adjustment may be made substantially independently of thesignal from the electro-optical pick-up system, since that signal forblack shade levels is an inappreciable fraction of the amplitude of thesignal from the screen generator 4!].

The pick-up system is then adjusted to a portion of the image of maximumbrightness, for example, white, and the tap SI of the voltage divider Min the output of the amplifier 73 is then adjusted to obtain the desiredmaximum penetration in accordance with the relationships of Fig. 1a. Theoperation of the system with the switch Hi5 connected to the externalsource of image signals N16 is in all respects the same, it only beingnecesary that such signals be derived from a pick-up system, eitherlocal or remote, operating synchronously with the pick-up carriage 22 ofFig. 1.

By way of example only, there may be given the 14 followingspecifications of one machine constructed in accordance with theinvention and providing satisfactory operation:

Screen 65 lines per inch Screen frequency 350 cycles per second Speed ofcylinders Ill, I2 50 R. P. M.

Lead l/65 Mesh l- 65V? Stylus 24 Radial to cylinder Stylus taper angle75 Thus, there is provided by the invention a machine for producing on aplate a screened relief pattern from an image sheet which virtuallyeliminates all skill or technique previously required to produce half-tone engravings. Furthermore, the machine of the invention producessuch plates in only a small fraction of the time required forconventional photo-engravings. For example, it has been found possibleto produce a plate 8 x 10" of 65 screen in eighteen minutes. The machineis capable of extreme accuracy of reproduction of intermediate shadevalues between full black and full white. At the same time, allchemicals and necessary facilities for handling them are eliminated. Bythe use of the stroboscopic viewer as described, it is possible todetermine in advance the desired contrast range of the resultant plate.This is in marked contrast to the conventional chemical processes whichgenerally require repeated trials before the desired contrast range isobtained. Further, by the simple operation of switch Hi5 of Fig. 5, itis possible to adapt the machine of the invention to operation fromimage-representing signals received by radio or wire from remotesynchronously scanned sources.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is:

1. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: a first cylinder for supporting a plate; a second cylinderfor supporting an image sheet; means for rotating said cylinderssynchronously; a first reciprocable carriage including an electroopticalpick-up system disposed for scanning an image sheet on said secondcylinder; a second reciprocable carriage including a plate-deformingtool disposed for scanning a plate on said first cylinder; meansresponsive to the output of said pick-up system for actuating said tool;means for reciprocating said carriages synchronously; an electricalscreen generator including a rotor element driven synchronously withsaid cylinders and an independently rotatable stator; and means forrotating said stator at a speed of a lower order of magnitude than saidrotor elesheet; means for rotating said cylinders; a first reciprocablecarriage including an electro-optical pick-up system disposed forscanning an image sheet on said second cylinder; a second reciprocablecarriage including a plate-deforming tool disposed for scanning a plateon said first cylinder; means responsive to the output of said pickupsystem for actuating said tool; means for reciprocating said carriagessynchronously; an

electrical screen generator including a rotor element drivensynchronously with said cylinders and an independently rotatable stator;and means for rotating said stator at a fraction of the speed of saidcylinders equal to one half the ratio of the speed of said cylinders tothe screen frequency; the output of said generator being connected tomodulate the output of said pick-up system.

3. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: a first cylinder for supporting a plate; av second cylinderfor supporting an image Sheet; means for rotating said cylindersisochronously; a first reciprocable carriage including anelectro-optical pick-up system disposed for scanning an image sheet onsaid second cylin der; a second reciprocable carriage including aplate-deforming tool disposed for scanning a plate on said firstcylinder; means responsive to the output of said pick-up system foractuating said tool; means for reciprocating said carriagesisoohronously; an electrical screen generator including a rotor elementdriven directly by said shaft and a rotatable stator element; and aspeed-reducing gear connected to drive said stator from said shaft; theoutput of said generator being connected to modulate the output of saidpick-up system.

4. A machine for producing on a plate from sheet; means for rotatingsaid cylinders synchronously; a first reciprocable carriage including anelectro-optical pick-up system disposed for scanning an image sheet onsaid second cylinder; a second reciprocable carriage including aplate-deforming tool disposedfor scanning a plate on said firstcylinder; means responsive to the output of said pick-up system foractuating said tool; means for reciprocating said carriagessynchronously; said pick-up system including a light source; anda-source of pulsating current of screen frequency connected to modulate.said light source synchronously with the scanning of the image sheet.

5. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: a first cylinder for supporting'a plate; a second cylinderfor supporting an image sheet; means for rotating said cylinders-synchronously; a first reciprocable carriage including an electro-opticalpick-up system disposed for scanning an image sheet on said secondcylinofpulsating 'current. ofscreen frequency 30011;

is nected to modulate the excitation of said lamp synchronously with thescanning of the image sheet.

6. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: a first cylinder for supporting a plate; a second cylinderfor supporting an image sheet; means for rotating said cylinderssynchronously; a first reciprocable carriage including anelectro-optical pick-up system disposed for scanning an image sheet onsaid second cylinder; a second reciprocable carriage including aplate-deforming tool disposed for scanning a plate on said firstcylinder; means responsive to the output of said pick-up system foractuating said tool; means for reciprocating said carriagessynchronously; said pick-up system including a light source; a periodicpotential generator of screen frequency; and a power amplifier forgenerating a periodic current synchronous with said periodic potentialand connected to modulate said light source synchronously with thescanning of the image sheet.

7. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable .ior image reproduction by printing processescomprising: a first cylinder for supporting a plate; a second cylinderfor supporting an image sheet; means for rotating said cylinderssynchronously; a first reciprocable carriage including anelectro-optical pick-up system disposed for scanning an image sheet onsaid second cylinder; a second reciprocable carriage including aplate-deforming tool disposed for scanning a plate on said firstcylinder; means responsive to the output of said pick-up system foractuating said tool; means for reciprocating said carriagessynchronously; said pick-up system in-- cluding a gaseous electricaldischarge lamp; a periodic potential generator of screen frequency; and'a power amplifier for generating a periodic current synchronous withsaid periodic poten tial and connected to excite said lamp synchronouslywith the scanning of the image sheet. .8. In a machine for producing ona plate from an image sheet a relief pattern suitable for imagereproduction by printing processes and including a pair of synchronouslyrotatable cylinders for individually supporting a plate and an imagesheet and a pair of reciprocable carriages individually including apick-up system and a plate-deforming tool for respectively scanning saidimagesheet cylinder and said plate cylinder, a mechanism forreciprocating said carriages synchronously in opposite directions toobtain an inverted relief pattern comprising: a pair of spaced pulleys;a tensioned inelastic belt-supported on said pulleys; one of saidcarriages including means for looking it to one run of said belt and areleasable clamp on the other of said carriages disposed to engage theother run of said belt.

9. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of synchronously rotatable cylinders for individuallysupporting a plate and an image sheet and a pair of reciprocablecarriages individually including a pick-up system and a platedeformingtool for respectively scanning said image-sheet cylinder and said platecylinder, a mechanism for reciprocating said carriages synchronously inopposite directions to. obtain an inverted relief pattern comprising: apair of spaced-pulleys; .a tensioned steel tape supported 17 on saidpulleys; one of said carriages including means for locking it to one runof said tape and a releasable clamp on the other of said carriagesdisposed to engage the other run of said tape.

10. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of rotatable cylinders for individually supporting aplate and an image sheet and a pair of reciprocable carriagesindividually including a pick-up system and a plate-deforming tool forrespectively scanning said image-sheet cylinder and said plate cylinder,a common drive shaft for said cylinders including a disengageablecoupling; a mechanism for reciprocating said carriages synchronously inopposite directions to obtain an inverted relief pattern comprising: apair of spaced pulleys; a tensioned inelastic belt supported on saidpulleys; one of said carriages including means for looking it to one runof said belt and a clamp on the other of said carriages disposed toengage the other run of said belt and releasable to permit independentadjustment of said other carriage upon disengagement of said coupling.

11. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of synchronously rotatable cylinders for individuallysupporting a plate and an image sheet and a pair of reciprocablecarriages individually including a pick-up system and a plate deformingtool for respectively scanning said image-sheet cylinder and said platecylinder, a positioning and actuating mechanism for said plate-deformingtool comprising: a tool actuating assembly including a plate-deformingtool; means for determining the neutral position of said tool assembly;electromagnetic means connected to respond to the output of said pick-upsystem for actuating said tool; and means for producing a pulsatingexcitation of said actuating means at a screen frequency; the amplitudeof said pulsating excitation being so proportioned to the constants ofsaid actuating means that the mean penetration of a plate by said toolis of the same order of magnitude as the neutral separation of said tooland its plate.

12. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of synchronously rotatable cylinders for individuallysupporting a plate and an image sheet and a pair of reciprocablecarriages individually including a pick-up system and a plate-deformingtool for respectively scanning said image-sheet cylinder and said platecylinder, a positioning and actuating mechanism for said plate-deformingtool comprising: a tool actuating assembly including a plate-deformingtool; means for determining the neutral position of said tool assembly;electromagnetic means connected to respond to the output of said pick-upsystem for actuating said tool; and means for producing a pulsatingexcitation of said actuating means at a screen frequency; the amplitudeof'said pulsating excitation being so proportioned to the response ofthe pick-up system that the minimum penetration of said toolcorresponding to one shade extreme in said image is of the order ofone-fifth its maximum penetration corresponding to the other shadeextreme.

13. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of sychronously rotatable cylinders for individuallysupporting. a plate and an image sheet and a pair of reciprocablecarriages individually including a pick-up system and a plate-deformingtool for respectively scanning said image-sheet cylinder and said platecylinder, a positioning and actuating mechanism for said plate-deformingtool comprising: a tool actuating assembly including a plate-deformingtool; means for determming the neutral position of said tool assembly;electromagnetic means connected to respond to the output of said picK-upsystem for actuating said tool; and means for producing a pulsatingexcitation of said actuating means at a screen frequency; the speed ofsaid cylinders being so related to the frequency of saw. excitation thatthe peripheral travel of said cylinders during one period 01 saidexcitation is approximately twice the desired llne spacing.

14. In a machine for producing on a plate from an image sheet a reliefpattern suitable for image reproduction by printing processes andincluding a pair of synchronously rotatable cylinders for individuallysupporting a plate and an image sheet and a pair of reciprocablecarriages incividually inclucnng a pick-up system and a platedeiormlngtool 101' respectively scanning said;

plate cyllnder and said image-sheet cylinder, a positioning andactuating mechanism for said plate-aelorming tool comprising; a toolactuating assembly including a plate-deforming tool; means I01 biasingsaid tool assembly into engagement with said plate cylinder; said toolassembly including an adjustable shoe engaging a plate on said platecylinder for determining the neutral position of said tool;electromagnetlc means connected to respond to the output of said pick-upsystem for actuating said tool; and means for producing a pulsatingexcitation of said actuating means at a screen frequency.

15. A machine ror producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising; plate ,and image-sheet supports; means including anelectro-optical pick-up system'for scanning an image sheet on itssupport; means including a plate-deforming tool for scanning a plate onits support synchronously with said first scanning means; meansresponsive to the output of said pick-up system for actuating said tool;a periodic electrical screen generator connected to modulate the outputof said pick-up system; and means for adjusting the output of saidgenerator to adjust the minimum deformation of said plate correspondingto the black level of an image sheet.

16. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: plate and image-sheet supports; means including anelectro-optical pick-up system including a light source for scanning animage sheet on its support; means including a plate-deforming tool forscanning a plate on its support synchronously with said first scanningmeans; means responsive to the output of said pick-up system foractuating said tool; a periodic electrical screen generator connected tomodulate said light source; and means for applying an adjustable portionof the output of said generator to said tool actuating means to adjustthe minimum deformation of said plate corresponding to the black levelof an image sheet.

17. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable 19 for image reproduction byprinting processescomprising: plate and image-sheet supports; means including.an-electro-optical pick-upsystem including a light source for scanningan 20 a. second amplifier coupled to said generatory means for combiningthe outputs of said ampli fier's; means responsive to said combinedoutputs for actuating said tool; means for adjustingthe image sheet onits support; means including a 5 output of said generatoramplifier-toadjust-the plate-deforming. toolfor scanning a plate 0n-its supportsynchronously with said first scanning means; a first amplifier coupledto the output of said pick-up system; a. periodieelectrical screenenerator; a second amplifier-coupled to= saidsaid plateucorresponding tothe: white level offan generator; and means responsive-jointly-totheoutputs of said amplifiers for actuating said tool.

18. A- machine'for producing-on a plate'irom an image sheet a screenedrelief pattern suitable-- minimum deformation of said platecorresponding to theblacklevel of an imagesheet; and means for adjustingthe output. of said pick-up system amplifier to adjust the maximumdeformation of image sheet.

22.. Amachineior producingona' platefrom an. image sheet a. screenedrelief pattern suitable for image reproduction by printing processescom:-

for image reproduction byprinting processes prising: plate.-andimage-sheet supports; means comprising; plate and image-sheetsupports; means including anelectro-optical pick-up sys-- tem includinga light source for scanning an; image sheet on its support; meansincluding a including. an electro-opticak pick-up system: for scanningan image sheet on. its support; means including a plate-deforming toolfor; scanning. a. plate on its support synchronously with said: firstplate-deforming tool -for scanning-aplate on its scanning means meansresponsive to. the output support synchronously with said -firstscanning means;- a firstamplifier coupled-to. the outputot said pick-up.system; a .periodie'electrical screen I generator; a secondamplifiercoupled to said of said pick-up system-for actuating said tool;a source of periodic potential connected to modulate the. outputof said.pick-up: system and means responsive to the'failure of saidsource foractuatgenerator; means for combining adjustable por-. ing said tool toan inoperative position.

tions of the outputs of said amplifiers; :and meansresponsivetosaid-combined outputsior actuating said tool.

1-9. A machine for producing 'ona plate from 23. A. machine forproducing. on a plate from an image-sheet a: screened relief patternsuitable for image reproduction by printing processesoomprising: plateand image-sheet supports; means an imagesheet a screened relief patternsuitable luding a electro-olfltical p fi p System for forimagereproduction. by printing processes comprising: plateandimage-sheet supports; means including an. electro optical pick-up sys-.tem for scanning an image sheet on its support meansincluding aplate-deforming tool for scans. ning a plate on: its supportsynchronously. with said first scanning means; means responsive: to theoutputof said: pick-up system for actuating said tool; a periodicelectrical screen generator connected to modulate: thev output: orsaid-pick-up. system; and means for adjusting the outputof said pick-upsystem to adjustthe maximum deformation ofsaid-plate. correspondingtouthe. white level of an image sheet.

20. A- machine for producingon a. plate from an image sheet a screenedrelief pattern suitable.

said tool, a periodic electrical screengenerator- 55 connected tomodulate the output of said pick-upsystem; means for adjusting theoutput ofsaid generatortoadjust the minimumdeformation of said platecorresponding to the black-level'of anscanning an image. sheet on itssupport; meansineluding a plate-deforming tool for scanning: a plate onits support synchronously with said first scanning means; meansfor'biasing saidgtool to an 35 inoperative position; a normally excitedelectro- 24. A machine for producingan a plate. from an image sheet ascreened relief pattern suitable for image reproduction byprintingprocesses comprising: plate-and image-sheet supports; meansincluding an. electro-optical pick-up system for scanning an image sheeton its support; means includingv a plate-deformingtool for scanning aplate on its support synchronously withsaid first scanning means; meansincluding an amplifier responsive to. the output of said pick-up system.for. actuating said tool; a filter network coupled to said. amplifierfor eliminating the onset. of variations. of the mean. brightness of.an. imagesheet on the mean position of saidtool; and a source ofperiodic potential of screen frequency connected to modulate the outputof said pickup system.

25. A machine for producing on a. plate from-- imagesheet? meansfor'adj'usfing fid an image sheet a screened relief pattern suitable ofsaid pick-up system-substantiallyindepend ently to adjust the maximum:deformation of said plate corresponding to thewhite level of an imagesheet.

for image reproduction by printing processes comprising: plate andimage-sheet supports; means including an electro-optical' pick-up,system'for' scanning an image sheet'on itssupport-y means A machine forproducingon platecf'rlom" Bdincludinga plate-deforming tool for scanningaan. image: sheet: a screened relief pattern suitable for image- 1'eproduction byprinting processes comprising:- plate andimage-sheetsupports;- means including anelectro-optical pick-up systemplate on its support synchronously with saidfirst scanning means; meansincluding an amplifier responsive totheoutput of saidpick-upsystemactuating said tool; a low-pass inverse feed-back in lu ial ht r e f s nin n ima mJnetwork coupled to said amplifier-foreliminating sheet on. its support; means. including a plate. deformingtool. for scanning. a plate on-itssupport synchronously with: said firstscanning: means a frst amplifijer coupled: to the output of said'pickthe efiect of variations of the mean brightnessof an image sheet onthe meanposition' of said tool ;-and a source of periodic potential ofscreen frequency connected to modulate the output of up. systenn:aperiodicelectricalLscreen generatog: 51said-pick-up-system.

26. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: plate and image-sheet supports; means including anelectro-optical pick-up system for scanning an image sheet on itssupport; means including a plate-deforming tool for scanning a plate onits support synchronously with said first scanning means; meansresponsive to the output of said pick-up system for actuating said tool;a source of periodic potential of screen frequency connected to modulatethe output of said pickup system; and a stroboscopic viewer ior saidplate including a light source energized from said source.

27. A machine for producing on a plate from an image sheet a screenedrelief pattern suitable for image reproduction by printing processescomprising: plate and image-sheet supports; means including anelectro-optical pick-up system for scanning an image sheet on itssupport; means including a plate-deforming tool for scanning a.

plate on its support synchronously with said first scanning means; meansresponsive to the output of said pick-up system for actuating said tool;a source of periodic potential of screen frequency connected to modulatethe output of said pickup system; a portable microscope adjustable forfocusing on a plate undergoing deformation and including a stroboscopiclight source; and a circuit for exciting said light source from saidperiodic source.

JOHN A. BOYAJEAN, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,063,614 McFarlane Dec. 8, 19362,079,970 Speed May 11, 1937 2,179,002 Washington, Jr. Nov. 7, 19392,489,691 Washington Nov. 29, 1949

